Most multimillionaires in the U.S. have a middle-class background and built their wealth gradually through hard work and buy-and-hold investing, according to the 2016 U.S. Trust Insights on Wealth and Worth released Monday.

The wealthy are a diverse group of people who nevertheless have a lot in common, according to the survey of 684 people with at least $3 million in investable assets.

“Perceptions of the wealthy in history and popular culture have been painted with a broad brush that doesn’t reflect the majority of financially successful people in society,” said Keith Banks, president of U.S. Trust.

The wealthy are an “increasingly diverse group of men and women of all ages and backgrounds. Their advantage in life is not rare financial privilege, but rather basic values, discipline and sense of potential shaped by family from an early age, which equipped them to make the most of every opportunity,” he said.

According to the survey, which was equally divided among people with $3 million to $5 million, $5 million to $10 million and more than $10 million, 77 percent came from middle class or lower backgrounds, including 19 percent who grew up poor. They earned wealth over time, most of it through income from work and investing.

Eighty-six percent made their biggest investment gains through long-term buy-and-hold strategies, traditional stocks and bonds (89 percent) and a series of small wins (83 percent) versus taking big investment risks.

Almost 60 percent of the high-net-worth keep more than 10 percent of their investment portfolios in cash positions and 20 percent have more than one fourth of their money in cash, partly to enable them to invest in sudden market ups or downs.

A strong tradition of family values and a desire to give back to the community through philanthropy are two traits that were evident across generations and across levels of wealth, the survey shows.

“The one common thread that cut across all generations was the importance and impact of family values as key contributors to success,” said Chris Heilmann, chief fiduciary executive of U.S. Trust. “As such, today’s advisors should be mindful of that focus to engage in values-based planning conversations with their clients.”

A common denominator among all those surveyed is a consensus among the wealthy that it is important to contribute in a meaningful way to society, the economy and strong communities, according to the survey.